Method and apparatus for multicolor printing



Sept. 29, 1970 MAKQTQ TANAKA ETAL 3,531,195

METHOD AND APPARATUS FOR MULTICOLOR PRINTING Filed Sepfc. 27, 1967 2 Sheets-Sheet 1 5 FILTER DISK INVENTOR. Ksm YosH IDA BY MAK T 7 mm Knzwosm WAFME. Hmosm ITA GAY/A Sept. 29, 1970 MAKOTO TANAKA ET AL 3,531,195

METHOD AND APPARATUS FOR MULTICOLOR PRINTING Filed Sept. 27, 1967 v 2 Sheets-Sheet 2 INVENTOR. Kim Y sm 12/:

BY MAK 7 mm Mums/-11 lwnnmz Hmosm KITAG-AWA w. (FM @427 United States Patent Int. Cl. G03g 15/22 U.S. Cl. 355-4 12 Claims ABSTRACT OF THE DISCLOSURE A method of printing of multicolor copies from a multicolor original pattern, carried out in a quick and easy manner by multicolor electro-photographic printing technique which first renders light passing through or being reflected from a multicolor original pattern monochromatic through a filter device, and then performs formation of a latent image and development thereof for each monochromatic light of different colors on a rotating drum, on which a photoconductive insulating substance is coated or held. The abovementioned rotating body is so constructed that it commences irradiation and scanning of the multicolor original pattern by a light source, when the signal detector provided outside of the rotating body detects a signal generated from signal generator provided within the first-mentioned rotating body or another rotating body which rotates in contact with first-mentioned rotating body for every rotation of the drum. By continuous and successive rotation of this rotating drum, desired multicolor printing can be accomplished without accompanying any discrepancy in color. The invention also proposes an apparatus to accomplish this multicolor printing.

This invention is a continuation-in-part application of our co-pending application No. 384,314, filed July 22, 1964, entitled Method and Apparatus for Multi-Color Printing, and now abandoned.

This invention relates to improvements in multicolor printing technique. More specifically, the invention concerns a new method and apparatus for accomplishing multicolor printing without use of printing plate capable of performing easy positioning of color pictures, hence continuous and rapid operations.

At present, the most commonly used multicolor printing method is that wherein a silver halide emulsion color film is used. In addition, various other methods such as those, wherein special filter layers in multilayer or mosaic form and photosensitive layers are used have been proposed. However, these methods have not reached the stage of wide use because of high cost or complexity of process, materials and apparatus.

The multicolor printing method generally used involves, essentially, the processes of multicolor separating the original image pattern, making a plurality of plates, and printing by superimposing images by means of these plates. Each of these processes requires a large number of steps. Furthermore, positioning is difiicult, whereby many trial proofs are necessary. Thus, the entire method requires a complicated process and apparatus. Therefore, this method cannot be considered to be a generally feasible and inexpensive method.

In view of the circumstances, various proposals have been made in the U.S. Pat. No. 3,057,520, No. 3,060,020, No. 3,253,913, and others, concerning multicolor printing using electrophotographic methods. However, none of these prior arts proposes easy position of color picture 3,531,195 Patented Sept. 29, 1970 and continuous and rapid operations as proposed in the present application.

The present invention, in its broad aspect, contemplates the elimination of such difficulties as described above. More specifically, the present invention contemplates a method and apparatus for accomplishing multicolor printing without use of printing plates, whereby multicolor printing can be accomplished from any kind of original image pattern irrespective of whether it is a negative or a positive, or whether it is transparent or nontransparent.

It is a primary object of the present invention to pro vide a method and apparatus, by which positioning of color pictures can be accomplished quite easily and without failure.

It is another object of the invention to provide a meth od and apparatus of the above character, whereby multicolor printing can be carried out on ordinary paper.

It is still another object to provide an apparatus capable of automatically carrying out the entire multicolor printing process.

It is a further object to provide a method and apparatus of the above stated character which requires only simple and easy process steps.

It is still other object to provide a method and apparatus capable of performing quick, continuous multicolor printing.

It is still further object to provide an apparatus for the above stated objects which can be miniaturized and, moreover, is relatively inexpensive.

The specific nature, principle, and details of the invention will be more clearly apparent by reference to the following description with respect to preferred embodiments of the invention, taken in conjunction with the accompanying drawings, in which like parts are designated by like reference characters, and in which:

FIG. 1 is partly schematic sectional view of a part of a circuit construction showing one embodiment of the multi-color printing apparatus according to the invention;

FIG. 2 is a planar view showing an interchangeable filter device of the apparatus shown in FIG. 1; and

FIG. 3 is a schematic sectional view showing another embodiment of the invention.

Referring now to FIG. 1, there is shown one embodiment of the multicolor printing apparatus of the invention, in which an original image pattern 1 such as a document, a reference book, or a photographic film to be reproduced in print is held in a position to be illuminated by a light source 2. The resulting reflected light from the original pattern 1 is caused to pass through a slit 3 and be directed in a certain definite direction by light control systems 4 and 6 consisting of lenses, mirrors, and other component parts. For the light control system 4, a lens is used such as an Aponikkor lens manufacured by Nippon Kogaku Kabushiki Kaisha (Japan Optical Co., Ltd), which is provided with a variable aperture stop or a shutter for controlling the passage of light through the lens. For the other light control system 6, a lens to correct chromatic aberration is used as an example. Even in this case, the variable aperture stop or the shutter is provided with the system. However, this light control system 6, can be dispensed with. At one point in the optical path of this light control system, there is positioned a filter plate 5 (shown as a disk in this example), Which is rotated by a filter plate driving device 5,,. The filter plate or disk is in stoppage during exposure, and, when one exposure due to a filter is complete, it changes the filter from one to the next. The rotation of the filter disk 5 is carried out by operating the driving device 5,.

A ground rotating drum 8 is so positioned that an optical pattern of the originals is exactly focussed on the surface of the printing paper 10 held on the drum 8 with the consequence that the light which has passed through the slit 7 and is directed to the printing paper 10 by means of the light control system 6 is inevitably brought to a focus on the printing paper 10. About this rotating drum 8, there are disposed a paper feeder 9 for supplying onto the peripheral surface of the drum 8 a printing paper (electrofax paper) 10 having on its surface a coating of a photoconductive insulating material or composed of a photoconductive insulator, a charging device 12 to apply uniform electrostatic charge to the printing paper 10, developing devices 13, 14, 15, and so forth for developing by means of toners capable of accomplishing development of respectively different colors, which are disposed radially on the turn table with the rotating axle as its center, a fixing apparatus 17 for fixing the toner image on the printing paper and a signal detector 18 adapted to operate co-operatively with a signal generator 18 provided on a drum 8. The drum 8 is provided with a device 11 which secures by means of for example vacuum suction the printing paper on the surface of the drum 8 so that its relative position may not change until completion of the printing operations. The signal generator 18 and signal detector 18 are so preset that, when they assume a predetermined relative position, they cause light reflected from the original pattern 1 to be projected onto the surface of the printing paper 10 on the drum 8.

In the foregoing example, a metal member fixed to the drum 8 and a micro-switch fixed outside of said drum 8 are used for the signal generator 18 and the signal detector 18 respectively. However, besides this, a spot light lamp, for example, can be used as the signal generator, and a photo-sensitive device such as photocell or the like as the signal detector 18,. In the latter case, the agreement in position between the two components is detected by incidence of light from the spot light lamp into the photosensitive device.

The device is further provided with an alternatingcurrent power source 22, a magnet 23, switches 24, 25 to open and close by the operations of the magnet 23, a driving apparatus 26 for the light source 2 and the light control system 4, a switch 27 to stop irradiation of an original pattern, an exchanging device 29 for exchanging the development devices, an actuating circuit 30 for actuating the filter plate driving device and the exchanging device 29. Besides, by provision of a spring device 31 for restoration of the light source 2 and the light control system 4 to their home positions, it is possible to carry out various kinds of continuous operations as well as positioning of image due to respective monochromatic light. These component devices can be installed in a dark place in case of necessity.

FIG. 2 is a front view of a filter plate 5, in which numerals 51, 52, 53, and 54 are filters of respectively different colors. The plate is rotatable on the rotating axle as its center.

Next, the operations of the multicolor printing apparatus according to the present invention are explained in reference to the accompanying drawing. At first, after the filter plate 5 sets a first color filter in the light path between the light control systems 4 and 6, and the exchanging device 29 set one developing device, for example, one as indicated with a reference numeral 13, the rotating drum 8 commences its rotation. A printing paper 10 is then fed by a paper feeding device 9 to the drum 8 and is wound and fixed around the drum 8 in rotation by a paper securing device 11 (the securing of the paper is also possible while the drum is in stoppage). The printing paper 10 thus secured on the drum 8 is uniformly charged by the electrostatic charging device 12 with rotation of the drum 8. Thus, in the state of the drum 8, on which electrostatically charged printing paper 10 is secured, being in rotation, when a metal piece of the signal generating device 18 causes a microswitch of the signal detector 18 to operate, electric current fiows through the magnet 23 to actuate the switches 24, 25 in a state of the switch 27 being closed,

whereby the driving device 26 commences operation and the light source 2 and the light control system 4 begin to shift.

At this time, if arrangement is so made that the light source 2 is simultaneously made operable, and that one end of the printing paper 10 comes to the position of the slit 7 at the time "when the light control system 4 commences shifting, the projection of the original pattern can be carried out in synchronism with the rotation of the rotating drum 8. As the drum 8 rotates, the microswitch of the signal detector 18 opens. However, since a closed circuit has already been formed by the magnet 23 and the switches 24, 27, the operation of the light source 2 still continues. As the light source 2 shifts, light which is reflected from the original pattern. 1 subjected to scanning is sequentially projected on the printing paper 10 held on the rotating drum 8 through the slit 3, the light control system 4, the filter plate 5, another light control system 6, and the slit 7. In this case, the light source 2, the slit 3, the light control system 4 and, if necessary, another light control system 6 are movable along with the scanning over the original pattern (these component members will therefore be called hereinafter as a movable optical system). During scanning over the original pattern, the light which is reflected from the original pattern can be always projected into the slit 7. This movable optical system operates in synchronism with the rotating drum 8 which holds the printing paper 10' thereon. During operation, the filter plate 5 remains still and the light reflected from the original pattern 1 is projected onto the printing paper 10 through one of the filters in the filter plate 5 such as, for example, a filter 51 as shown in FIG. 2 so that a monocolored pattern of the original pattern depending on the color of the filter in use may be projected onto the paper and that a latent image be formed thereon.

When irradiation of the original pattern 1 from the light source 2 is accomplished, supply of power to the driving apparatus 26 is interrupted by the switch 27 which has previously been so made that it becomes open on completion of scanning, whereby the light source 2 and the light control system 4 stop their operation and return to their initial position by the spring device 31. There is provided a switch 28 which is so constructed as to be actuated simultaneously with opening of the switch 27, the filter exchanging device 5 is operated to exchange the filters by this switching action. In this case, the switch 28 acts to start the circuit 30 for operating exchange of the filters and the developing devices. When the paper 10 reaches a predetermined position where the developing devices are located while the drum 8 is rotating, color development is performed by one developing device, for example, the developer 13 capable of developing monocolor image corresponding to one filter used such as 51 as shown in the drawing. During development of color by a particular development device such as one designated by reference numeral 13, the other developing devices 14, 15, and so on do not perform their functions. That is, upon completion of the development by each development device, the power is connected to the exchanging device 29 for the developing device through the circuit 30, whereby changing of the developing device is carried out. This changing action can be performed, for instance, by first separating a turntable from the drum 8, and then rotating the table. The development by the respective developing devices is done by the method such as described in the US. Pat. No. 3,186,838. It is also possible that, at the time of changing the developing device, the filter can be changed. The circuit 30 can be used not only for changing the filter and the developing device, but also for controlling operations such as fixing, electrostatic charging (the second color et seq.), and so forth. It is preferable to use, in this circuit 30, a timer which presets the time period suflicient to complete the developing operation by the developing device and to allow the switch 28 to control commencement of the operation of the timer.

When the printing paper thus developed arrives at the position of the fixing device 17, the fixation of the developed image is carried out, whereby the first step of printing is accomplished. The printing paper 10 which has undergone the first step of printing is again electrostatically charged uniformly by means of the electro static charging device 12 and then it is sent to the second step of printing. At this stage, the movable optical system has been returned to the original state, and the filter plate 5 has been caused to rotate by a filter plate rotating device 5 to change the filter from one to another, such as from 51 to 52. The development device has also been simultaneously changed to one such as, for example, the color developer 14, corresponding to the filter 52, whereby the second step of printing can be performed in a similar manner to the first step of printing. Thus, after repetition of projection, development, and fixing for required number of times, depending on the number of color filters used the printing paper 10 is separated from the drum 8 by the printing paper securing device 11, whereby a multicolor printing copy can be obtained from a multicolor original pattern.

The electrostatic charging device, the fixing device, etc. may also be constructed in such a manner that they commence their operation individually in accordance with rotation of the drum by being provided respectively with, for example, a microswitch to be engaged with a signal generating means provided on the drum.

While, in the case of the above-described example, the original pattern 1 is illuminated by light projected thereon, it is also possible to use a light transmission method by suitably arranging the movable optical system. For the original image pattern, a negative or a positive can be used for reproductive printing according to this invention irrespective of whether the pattern is transparent or nontransparent. Moreover, by suitably selecting the filters and developing toners, multicolor printing is possible according to the two-color method, the three-color method, or a multicolor method utilizing many more kinds of colors.

Furthermore, while in the case of the above described example, it is necessary to use a photoconductive insulating printing paper, it is also possible to use ordinary paper for the printing paper by using an apparatus as exemplified by another embodiment of the invention as shown in FIG. 3. Briefly stated, this method comprises forming a projected image of the original pattern on a xerographic drum, developing the image, transferring the image so developed onto a printing paper (ordinary paper) secured on a paper holding drum which corresponds to the drum 8 of the embodiment of FIG. 1 and cooperates with the xerographic drum, and then fixing the transferred image.

Referring to FIG. 3, the parts designated by reference numerals 1 through 18, and 29 inclusive are the same as those of corresponding designations in the apparatus shown in FIG. 1. (The electrical circuit is exactly the same as that of FIG. 1.) The apparatus of FIG. 3 is provided additionally with a xerographic drum 19 consisting of a grounded (or earthed) drum made of metal or insulating material having on its peripheral surface a coating of a photoconductive insulating material such as amorphous selenium or an organic photoconductor, a cleaning device 20 for removing surplus toner adhering to the surface of the drum 19, and a trans-fer device 21 for transferring to a printing paper 10 secured onto the drum 8 the toner adhering to the image of the pattern 1 on the drum 19, the printing paper 10,, consisting of paper of ordinary quality. For the cleaning device 20, a rotational roll, around which a flix of rabbit, for example, is wound, is used, and, by rubbing the surface of the drum 8 with this roll, the surplus toner can be perfectly removed. The removed toner is trapped into a vacuum sucking device.

In the operation of this apparatus, the reflected light directed by the movableoptical system from the original pattern 1 is projected onto the peripheral surface of the xerographic drum 19 which has been uniformly charged by the charging device .12 to form a latent image on this drum 19. The latent image so formed is developed by a developing device, for example, device 13, and then transferred by the transferring device 21 onto the printing paper 10,, supplied from the paper feeder 9 and secured to the rotating drum 8 by paper securing device 11. The transfer device 21 is to transfer onto the printing paper 10,, the latent image formed by the toner on the drum 19, and it comprises a power source and electrodes to impress an electric field between the drum 19 and the printing paper 10,, a contact portion thereof. By the electrostatic field thus created, the toner image is transferred to the printing paper 10,,. The image so transferred is then fixed by the fixing device 17. After this image transfer, the toner remaining on the drum 19 is removed by the cleaning device 20. Thereafter, the projection, developing, and fixing of the second step and the succeeding steps are similarly carried out.

The projection of the original pattern and the changing of the filters and the developing devices are accomplished by means of the signal generator 18 and the signal detector 18, similarly as in the case of the example illustrated in FIG. 1. However, in this embodiment of FIG. 3 the signal generator 18 and signal detector 18a are so positioned that they are coupled together when the beginning end of the printing paper 10a held by the paper securing device 11 on the drum 8 comes to a position where the arcuate distance of the beginning end from the contact portion on the drum 8 is the same as the arcuate distance between the contact portion and the image projected portion on the drum 19. Even in this case, it is possible that not only change of the filters and the developing devices, but also commencement of operations of the fixing device 17, electrostatic charging device 12, cleaning device 20, transferring device 21, etc. are made to be carried out after lapse of a preset time period from operation of a signal indicating completion over scanning of the multi-color original pattern as the reference standard. That is, the above-described embodiment of the invention differs from that shown in FIG. 1 in that, through the use of a xerographic drum 19, printing on ordinary paper is made possible, but in operation and effectiveness the two examples are similar.

In either case, half-tone printing is also possible by using devices such as mesh screen filters for the mesh screen process and in ordinary printing methods. Furthermore, developing may be carried out after transfer of electrostatic latent image instead of transfer of a toner.

The multicolor printing method and apparatus if this invention is, of course, not limited to the above described embodiments thereof, but other arrangements and construction of parts within the intended scope of the invention is possible. For example, a belt or a prismatic structure can be used in place of the rotating drum; or, instead of scanning the original pattern, the entire pattern can be projected in one operation. Furthermore, known xerographic techniques and optical techniques may be utilized in the present invention.

As described above, the multicolor method and apparatus of the present invention affords plateless printing without necessity of a large number of printing plates as in the case of conventional multicolor printing methods. Since coloration is determined by the colors of the filters and the colors of the toners, multicolor printing is possible from any kind of original pattern irrespective of its being a negative or a positive or its being transparent or non-transparent. Another advantage is that printing is possible on ordinary paper or on electrophotographic paper for ordinary black and white printing.

Furthermore, by the practice of this invention, the printing paper is, for example, wrapped around and secured to a drum, repeated cycles of exposure, developing, and fixing being carried out in accordance wtih the rotation as said drum, and the exposure is started when a signal generator provided at a preset position on the drum is coincidently aligned with a signal detector positioned outside of the drum at a preset position. Accordingly, the position of the printing paper relative to the position of the original pattern is constantly fixed throughout the entire process, and it is not necessary to carry out adjustment to hold the printing position, which has been a problem accompanying conventional methods. Therefore, special consideration and measures for placing the original pattern and printing paper in the apparatus are unnecessary.

Moreover, since the apparatus of this invention can be operated automatically after the mere placing of the original pattern in the correct position as in the case of ordinary monochromatic xerography systems, the apparatus can be easily handled. Since the construction is simple, the apparatus can be manufactured at low cost. It will thus be evident that the present invention affords a method and apparatus for multicolor printing which can be effectively applied to a wide range of uses.

What we claim is:

1. A multicolor electrophotographic printing process to obtain from a multicolor original pattern a multicolor copy corresponding to said original pattern, wherein light which is passed through or reflected from the multicolor original pattern is rendered into monocolor light, which is then projected to a photoconductive insulting substance which has been electrostatically charged beforehand so as to form a latent image thereon, and the latent image so formed is developed and fixed, the steps of which are successively carried out with respect to a plurality of monocolor lights of different colors, which process comprises the steps of:

(a) electrostatically charging a printing paper of pho- I toconductive insulating properties held on a rotating body;

(b) irradiating and scanning said multicolor original pattern by a light source when said rotating body is in rotation and after a signal detector provided outside of said rotating body has detected a signal generated from a signal generator provided within said rotating body, thereby forming a latent image on said printing paper;

(0) developing and fixing said latent image to accomplish the first step of color printing; and

(d) subsequently performing said respective operations for other monocolor light image formed by other different color filters through continuous rotation of said rotating body.

2. A multicolor electrophotographic printing process to obtain from a multicolor original pattern a multicolor copy corresponding to said original pattern, wherein light which is passed through or reflected from a multicolor original pattern is rendered into monocolor light, which is then projected to a photoconductive insulating substance which has been electrostatically charged beforehand so as to form a latent image thereon and the latent image so formed is developed, transferred, and fixed, the steps of which being successively carried out with respect' to a plurality of monocolor lights of different colors, which process comprises the steps of:

(a) electrostatically charging a photoconductive insulating substance coated on a first rotating body;

(b) irradiating and scanning said multicolor original pattern by a light source when said rotating body is in rotation and after a signal detector provided outside of a second rotating body which secures printing paper on its surface and rotates in contact with said first rotating body has detected a signal generated from a signal generator provided within the second rotating body, thereby forming a latent image on said photoconductive insulating substance;

(c) developing said latent image and transferring the same onto the printing paper held on said second rotating body;

(d) subsequently fixing said transferred image, thereby finishing the first step of color printing; and

(e) repeating said respective operations for other monocolor light images formed by other different color filters through continuous rotation of said first and second rotating bodies.

3. A multicolor electrophotographic printing apparatus of a type wherein light which is passed through or reflected from a multicolor original pattern is rendered into monocolor light, which is then projected to a photoconductive insulating substance which has been electrostatically charged beforehand so as to form a latent image thereon and the latent image so formed is developed, and fixed, the step-s of which being successively carried out with respect to a plurality of monocolor lights of different colors which comprises:

(a) means for irradiating the multicolor original pattern by a light source;

(b) means for scanning said multicolor original pattern by said irradiating means;

(c) means for projecting a light passed through or reflected from said multicolor original pattern in a constant direction;

(d) a filter plate accommodating a plurality of different color filters to render said light into a monocolor light and provided in the light path between said irradiating means and light projecting means;

(e) a rotating body to hold a printing paper of photoconductive insulating properties, on which a latent image is to be formed by the incident light;

(f) an electrostatic charging means for said printing paper disposed at a position facing to the peripheral surface of said rotating body;

(g) a plurality of developing means of different kinds of colors;

(h) a fixing means;

(i) means for exchanging said filters and developing means for each color in interlocking manner;

(j) a signal generator provided within said rotating body;

(k) a signal detector provided outside of said rotating body and operatively connected to said signal generator intermittently as said rotating body is in rotation to detect a signal from said signal generator; and

(l) actuating means operatively actuating said irradiating means and said scanning means to commence irradiation and scanning over the multicolor original pattern by the light source when said signal detector detects a signal from said signal generator,

whereby multicolor printing can be carried out by continuous rotation of said rotating body.

4. Apparatus according to claim 3 in which there are further provided a switch to operate when the irradiation and scanning by the light source is completed, and means for operating said means for changing the filters and developing means for each color immediately or some time after lapse of predetermined time by the operation of said switch.

5. A multicolor electrophotographic printing apparatus of a type wherein light which is passed through or refiected from a multicolor original pattern is rendered into monocolor light which is then rojected to a photoconductive insulating substance which has been electrostatically charged beforehand so as to form a latent image thereon and the latent image so formed is developed, transferred, and fixed, the steps of which being successively carried out with respect to a plurality of monocolor lights of different colors, which comprises;

(a) means for irradiating the multicolor original pattern by a light source;

(b) means for scanning said multicolor original pattern by said irradiating means;

(c) means for projecting a light passed through or reflected from said multicolor original pattern in a constant direction;

(d) a rfilter plate accommodating a plurality of different color filters to render said light into a monocolor light, and provided in the light path between said irradiating means and light projecting means;

(e) a first rotating body on which there is coated a photoconductive insulating substance where a latent image is to be formed by the incident light;

(f) an electrostatic charging means for said photo i conductive insulating substance disposed at a position facing to the peripheral surface of said first rotating body;

(g) a plurality of developing means for different kinds of color to develop the latent image formed on the photoconductive insulating substance coated on said first rotating. body;

(h) a second rotating body which holds printing paper on its surface and rotates in contact with said first rotating body;

(i) means for transferring the latent image on said first rotating body which has been developed on the printing paper;

'(j) means for changing said filters and developing means for each color in interlocking manner;

(k) a signal generator provided within said second rotating body;

(1) a signal detector provided outside of said rotating body and operatively connected to said signal generator intermittently as said rotating body is in rotation to detect a signal from said signal generator; and

(m) actuating means operatively actuating said irradiating means and said scanning means to commence irradiation and scanning over the multicolor original pattern by the light source when said signal detector detects a signal from said signal generator;

whereby multicolor printing is carried out by continuous rotation of said first and second rotating body.

6. \Apparatus according to claim 5, further provided with a switch to operate when the irradiation and scanning by the light source is completed, and means for operating said means for changing the filters and developing means for each color immediately or some time after lapse of predetermined time by the operation of said switch.

7. A multicolor electrophotographic printing apparatus comprising:

(a) a cylindrical drum rotatable at a constant speed and having sheet holding means for holding on the periphery thereof a sheet member, at least one surface of which is coated with a photoelectric insulating material;

(b) charging means disposed in close relation to said drum to electrostatically charge the photoconductive insulating coating of said sheet member held on the drum uniformily;

(c) cleaning means disposed in close relation to said drum for cleaning the photoconductive insulating coating before it is charged by said charging means;

(d) scanning means including a source of irradiation light and an optical lens assembly for operatively irradiating and scanning over a multicolor original pattern, from which a printed copy is to be reproduced in synchronism with the rotation of said drum, so as to project image thereof onto the photoconductive insulating coating of the sheet member which is previously charged uniformly, thereby forming an electrostatic latent image of said original pattern on the photoconductive insulating coating;

(e) filter exchanging means accommodating a plurality of different color filters for selectively interposing said filters one after another in the light path between said scanning means and said drum so that the image projected from said scanning means is rendered into a monocolor image depending one said one filter selected;

(f) developer exchanging means accommodating a plurality of developing means to effect developments of different color images corresponding to said different color filters, respectively, said developer exchanging means interchangeably coupling said developing means one after another to said drum in accordance with the selective interposition of the corresponding one filter in said light path for effecting development of the electrostatic latent image formed by corresponding one filter on said photoconductive insulating coating;

(g) fixing means disposed in close relation to said drum for fixing the latent image developed on the photoconductive insulating coating;

(h) a sheet position indicator including a signal generator and a cooperative signal detector, one of said signal generator and said signal detector being provided on said drum and the other being provided outside of said drum in such positions that they are coupled together when the sheet member held on the drum becomes confronted with said scanning means, so that said indicator generates an indication output when they are coupled together;

(i) first actuating means for rendering said scanning means in its actuated state in response to generation of the indication output from said indicator thereby effecting irradiation and scanning over the original pattern whenever the indication output is obtained; and

(j) second actuating means for actuating said filter exchanging means to exchange said filters in response to completion of the scanning operation of said scanning means, and for actuating said developer exchanging means to exchange the developing means some time after lapse of predetermined time from the completion of the scanning operation of said scanning means, whereby multicolor printed copy of the original pattern can be obtained on the sheet member by successive rotation of said rotatable drum.

8. Apparatus according to claim 7, in which said second actuating means includes a switch to be actuated when the irradiation and scanning by said scanning means is completed, a first actuating circuit for operating said filter exchanging means immediately in response to actuation of said switch, and a second actuating circuit having a delay time for operating said developer exchanging means some time after lapse of said delay time from the actuation of said switch.

9. A multicolor electrophotographic printing apparatus comprising:

(a) a first cylindrical drum rotatable at a constant speed and having a coating of a photoconductive insulating material on the periphery thereof;

(b) charging mean-s disposed in close relation to said first drum to electrostatically charge the photoconductive insulating coating of said first drum uniformly;

(c) cleaning means disposed in close relation to said first drum for cleaning the photoconductive insulating coating before it is charged by said changing means;

((1) scanning means including a source of irradiation, light and an optical lens assembly for operatively irradiating and scanning over a multicolor original pattern, from which a printed copy is to be reproduced in synchronism with the rotation of said first drum, so as to project an image thereof onto the photoconductive insulating coating which is previously charged uniformly, thereby forming an electrostatic latent image of said original pattern on the photoconductive insulating coating;

(e) filter exchanging means accommodating a plurality of different color filters for selectively interposing said filters one after another in the light path between said scanning means and said first drum so that the image projected from said scanning means is rendered into a monocolor image depending on said one filter selected;

(f) developer exchanging means accommodating a plurality of developing means to effect developments of different color images corresponding to said different color filters, respectively, said developer exchanging means interchangeably coupling said developing means one after another to said first drum in accordance with the selective interposition of the corresponding one filter in said light path for effecting development of the electrostatic latent image formed by said corresponding one filter on said photoconductive insulating coating;

(g) a second cylindrical rotatable drum having holding means for holding a sheet member on which a copy of said original pattern is to be reproduced, said second drum being operatively rotated in synchronism with and disposed in contact with said first drum so that a sheet member held by said holding member contacts the photoconductive insulating coating on said first drum;

(h) transferring means provided at the contact portion of said first and second drums for transferring the developed latent image on said photoconductive insulating coating of said first drum onto a sheet member contacted;

(i) fixing means adapted to said second drum for fixing the transferred image thereon;

(j) a sheet position indicator including a signal generator and a signal detector, one of said signal generator and said signal detector being provided on said second drum and the other being provided outside of said second drum in such positions thatthey are coupled together when an arcuate distance between said contact portion and the sheet member held by the holding means on the second drum becomes same as the arcuate distance between the contact portion and the light projected portion on the first drum onto which the image of the original pattern is projected, so that said indicator generates an indication output when they are coupled together;

(k) first actuating means for rendering said scanning means in its actuated state in response to generation of the indication output from said indicator, thereby effecting irradiation and scanning over the original pattern whenever the indication output is obtained;

(l) second actuating means for actuating said filter exchanging mean-s to exchange said filters in response to completion of the scanning operation of said scanning means, and for actuating said developer ex changing means to exchange the developing means some time after lapse of predetermined time from the completion of the scanning operation of said scanning means whereby multicolor printed copy of the original pattern can be obtained on the sheet member by successive rotation of said first and second rotatable drums.

10. Apparatus according to claim 9, in which said second actuating means includes a switch to be actuated when the irradiation and scanning by said scanning means is completed, a first actuating circuit for operating said filter exchanging means immediately in response to actuation of said switch and a second actuating circuit having a delay time for operating said developer exchanging means some time after lapse of said delay time from the actuation of said switch.

11. A multicolor electrophotographic printing apparatus comprising:

(a) means to irradiate a multicolor original pattern,

from which a multicolor copy print is to be reproduced;

(b) scanning means to perform scanning operation over said multicolor original pattern irradiated to obtain an image light representing a part of said original pattern under said scanning;

(c) a rotatable body operatively rotated in one direction and holding thereon a printing paper with a photoconductive insulating surface layer;

(d) electrostatic charging means disposed at a position facing to the peripheral surface of said rotatable body and to provide a uniform electrostatic charge to said photoconductive layer of said printing paper held on said rotatable body;

(6) means to project said image light obtained from said scanning means along a constant path to said printing paper which has been provided with the uniform charge;

(f) a plurality of different color filters selectively positioned one after another in said constant path of said image light to cause said image light to pass therethrough into different monocolor lights corresponding to colors of the filters selected, so that difi'erent kinds of monocolor latent images are formed on the photoconductive layer;

(g) a plurality of developing means provided in correspondence to said color filters to develop the different kinds of monocolor latent images formed, said developing means being selectively positioned one after another at a position facing to the peripheral surface of said rotatable body so as to provide their developing activities onto the latent images formed on the layer;

(h) fixing means disposed at a position facing to the peripheral surface of said rotating body to fix the monocolor developed images;

(i) means to exchange said filters and their correponding developing means in interlocking manner;

(j) a signal generator to enerate a signal;

(k) a signal detector to detect the signal generated by said signal generator when coupled to said signal detector, one of said signal generator and said signal detector being provided within said rotatable body and the other one being provided outside of said rotatable body to be intermittently coupled together;

(1) actuating means to commence actuation of said irradiating means and said scanning means, when said signal detector detects the signal from said signal generator and to maintain said actuation until said scanning means completes one scanning operation over the original pattern; and

(m) a control means responsive to the completion of the scanning by said scanning means to actuate said exchanging means;

whereby the different kinds of monocolor image lights are repeatedly projected on the printing paper at the same position by repeated contact between the signal generator and the signal detector as the rotatable body rotates, to thereby obtain a multicolor copy print.

12. A multicolor electrophotographic printing appara-.

tus comprising:

(a) means to irradiate a multicolor original pattern, from which a multicolor copy print is to be reproduced;

(b) scanning means to perform scanning operation over said multicolor original pattern irradiated to obtain an image light representing a part of said original pattern under said scanning;

(c) a first rotatable body operatively rotated in one direction and having thereon a layer of a photoconductive insulating substance;

((1) electrostatic charging means disposed at a position facing to the peripheral surface of said first rotatable body and to provide a uniform electrostatic charge to said photoconductive layer of said first rotatable body;

(e) means to project said image light obtained from said scanning means along a constant path to said first rotatable body;

(f) a plurality of different color filters selectively positioned one after another in said constant path of said image light to cause said image light to pass therethrough into different monocolor lights corresponding to colors of the filters selected, so that different kinds of monocolor latent image are formed on the photoconductive layer;

(g) a plurality of developing means provided in correspondence to said color filters to develop the different kinds of monocolor latent images formed, 1 said developing means being selectively positioned one after another at a position facing to the peripheral surface of said first rotatable body so as to provide their developing activities onto the latent images formed on the first rotatable body;

(h) a second rotatable body holding thereon a printing paper and operatively rotated in contact with said first rotatable body;

(i) transfer means provided at the contact position between said first and second rotatable bodies to trans- 20 fer the latent images thus developed on said first rotatable body onto the printing paper;

(j) fixing means disposed a a position facing to the peripheral surface of the second rotatable body to fix the transferred monocolor developed images;

(k) means to exchange said filters and their corresponding developing means in interlocking manner;

(1) a signal generator to generate a signal;

(m) a signal detector to detect the signal from said signal generator when coupled together, one of said 30 signal generator and said signal detector being provided within said second rotatable body and the other being provided outside of said second rotatable body so as to be intermittently coupled together;

(n) actuating means to commence actuation of said irradiating means and said scanning means, when said signal detector detects the signal from said signal generator and to maintain said actuation until said scanning means completes one scanning operation over the original pattern; and

(0) control means responsive to the completion of the scanning by said scanning means to actuate said exchanging means;

whereby the different kinds of monocolor developed images are repeatedly transferred onto the printing paper at the same position by successive rotation of said first and second rotatable bodies, to thereby obtain a multicolor copy print.

References Cited UNITED STATES PATENTS 2,566,264 8/1951 Tuttle et al. 95-2 2,571,697 10/1951 Evans 952 2,752,833. 7/1956 Jacob 96-12 X 3,045,644 7/1962 Schwertz 118637 3,057,720 10/1962 Hayford et a1. 961 3,060,020 10/1962 Greig 961.2 3,230,303 1/1966 Maconski et a1. 96-1 OTHER REFERENCES Parker et al., An Electrostatic Color Map Printer, J. of the SMPTE, October 1960, pp. 744-747.

Pennington, Electrostatic Procedures for Map Reproduction, presented at 2nd International Course for Map Printing and Reproduction October 1960, title page and pp. 12-22.

JOHN M. HORAN, Primary Examiner 

